Process of purifying zinc ore



Aug. 26, 193& o. GERLACH PROCESS OF PURIFYING ZINC ORE Filed Dec. 31,1927 4 Sheets-Sheet 1 E/KYJTTZZTW: JEQ ZZY I WW Aug. -5, 1930. OVGERLACHPROCESS OF PURIFYING ZINC ORE Filed Dec. 51, 1927 4 Sheets-Sheet 2TLLOOL aw Aug. 26, 1930. o, GERLACH 1,773,991

PROCESS. OF PURIFY ING ZINC ORE Filed Dec. 31, 1927 '4 Sheets-Sheet 305W Ganbcz/olv PROCESS OF PURIFYING ZINC ORE Filed Dec. 51, 1927 4Sheets-Sheet 4 ROASTED ORE COARSE LUMPS CHARGEH ACHINE H 9 ;I C1SCALPING +0 E #1 smrsnzo ORE +H Q COARSE MATERIAL .S CREEN'.

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' SCREEN COARSE. LUMPS 1 PARTLY 5 NTERED ORE E1 677157 0560/ Gar/6mJMA%O w y/z wz Patented Aug. 26, 1930 UNITED STATES PATENT OFFICE OSCARGERLACH, 0F PERU, ILLINOIS, ASSIGNOR TO MATTHIESSEN & HEGELER ZINC 00.,OF LA SALLE, ILLINOIS, A CORPORATION OF ILLINOIS BBOCESSOF PURIFYINGZINC ORE Application filed December 31, 1927. Serial No. 243,840.

This invention relates to an improved process of purifying zinc andother ores and to the apparatus employed in carrying on said process andits purpose is to provide improved means and an improved method for moreefficiently effecting the purification which has heretofore been carriedon chiefly by electrolytic means. The principal purpose of the inventionis to provide a method for removing from zinc sulfide, carbonate, orother zinc ores-the lead and cadmium compounds and other compounds whichare frequently present and which ordinarily volatilize readily when thezinc ore is heated.- A further object is to provide an improved methodof purifying zinc ores by the application of heat. Another object is toprovide an improved method of purifying zinc ores according to which thecrushed ore is heated in the presence of a reducing agent. Still anotherobject is to provide an improved method of purifying zinc ores by theapplication of heat in separate heating stages, the residue obtainedfrom the operation of one heating stage being treated in the nextheating stage of the process. An important feature of the invention isthe discovery that the purification of zinc ores may be effected by amodification of the sintering apparatus which is emplo ed with iron oresand the like. Other ob ects of the invention relate to various featuresof the process and apparatus which will'appear more fully hereinafter.

Zinc ore most frequentlyv exists in the form of zinc. sulphide (ZnS) andin the practice of the present invention this ore is first crushed to asufiiciently fine condition to enable it to pass through a ten meshscreen, that is, a screen having ten divisions to the inch. and thescreened ore is then roasted in the usual roasting furnace at atemperature of from 1600 degrees Fahrenheit to 1800 degrees Fahrenheitto remove therefrom the larger portion of the sulphur (about 90%),

roasting furnace is taken therefrom and' crushed and screened afterwhich it is put into a sintering machine through a hopper, preferablyalong with a quantity of previously treated ore which is taken from thedischarge of the same or another sintering machine. The crushed andscreened ore from the roasting furnace and the coarse materials from thedischarge of'the sintering.

machine are thoroughly wetted with water before being introduced intothe pans of the sintering machine to facilitate the passage of heatthrough the crushed material and to aid in the reducing process. The orewhich is thus placed in the pans of the sintering machine is conveyed inthese pans at a relatively low rate of speed, for example, at the rateof six inches per minute, and the ore is thus brought under a sinteringhood equippedwith gas burners or other burners for producing a hightemperature therein, preferably a temperature between 2600 degrees F.and 2800 degrees F. A number of burners are preferably provided in thishood, the first ones being fed with air and oil or gas to produce anoxidizing flame while the later ones of the series are fed with steamand oil or Water gas to form a reducing flame and to cause theproduction-of free hydrogen which is made use of in freeing the Zinc oreof the cadmium oxide therein. Preferably, a, two inch layer of line zincore is put on top of'a one-half inch layer of coarse ore. The object ofputting the coarse more with the result that the upper por-.

' tions of the ore in the sintering pans are flames. It would appearthat the lead and substantially freed of both lead and cadmiumcompounds. The lead is driven out of the layer of ore penetrated by theflames and collects partly in the ore beneath the same in the form ofsulphate (while partescapes as such through the fan and stack to theair), and the cadmium likewise is driven out of the upper layer andcollects partlyv in the lower 1a er in the form of sulphate and sulphidewhile art escapes. The zinc oxide in the upper ayer is not driven out inthe limited time during which the ore is exposed to the cadmium in theupper layer are reduced and then volatilized a recombine in the vaporousstate with sul hur and oxygen to form" the Sn] hates an sulphides in thelower layer. Thus, the upper portions ofthe crushed materials in thepans of the sintering machine are substantially freed ofcadmium and leadcompounds; According to the present invention, this upper portion of theore is scraped or otherwise removed from the lower layer of ore in thepans before the pans reach the end of their upper path of travel in themachine. The zinc ore which is thus removed is subsequently distilledwith carbon rated and returned to the inlet end of the machine asreferred to above for the protection of the pans and to prevent theclogging of the openings in the bottoms of the pans, while the finematerials are introduced into a hopper along with a quantity of carbon,preferably in the form of finely divided anthracite coal. The mixturedischarged from this hopper is then elevated by a conveyor,

F wetted with water, and fed into another after which the coarsematerials are returned to the inlet end of the second machine while thefine materials are mixed with carbon and fed to a third sinteringmachine. By carryon the process in a. number of successive stepssubstantially all of the zinc in the ore may be freed of the cadmium andlead compounds and at the same time the sulphur di-' oxide gas which isliberated in the several machines of the series may be drawn off andmade use of in the manufacture of sulphuric acid. The escaping vapors oflead and cadmium sulphates may also be saved (by a Cottrell separator)and made use of. Although various forms of apparatus might be employedin carrying on the process described above, there is illustrated in theaccompanying drawings an improved sinter-' ing machine which is adaptedfor that purpose. I

In the drawings, Figure 1 shows a side elevation of the sinteringmachine;

Fig. 1 shows a side elevation of a second sintering machine which isarranged to receive the discharge from the first sintering machine shownin Fig. 1;

Fig. 2 is an enlarged vertical section on the line 2-2 of Fig. 1;

Fig. 3 is an enlarged section through one of the cutting and scrapingdevices for removing materials from the upper parts of the sinteringpans, and

Fig. 4 is a diagram of the flow sheet of the'improved process carried onby the pres ent invention.

As illustrated in the accompanying drawings, the apparatus comprises twosintering machines 10 and 10*? which are shown in Figs. 1 and 1,respectively, and which are similar in construction so that adescription of one will sufiice for both. Each sintering machinecomprises a plurality of sintering pans 12 which are mounted to followan endless path of travel and which form a substantially continuousseries so that each pan is located closely adjacent to the next leadingand following pans of the series, except at the discharge end of themachine where a gap 13 is provided to allow the pans to drop a shortdistance to facilitate the dumping of the contents thereof. Thesintering pans 12 are supported by a frame 14 comprising a plurality ofvertical frame members 15 and a number of transverse frame members 16.This frame 14 serves as a support for certain track members which areprovided to coact with rollers 17 mounted to revolve on trunnions 18projecting laterally from opposite sides of the sintering pans 12, therebeing two rollersi17 at each side of each pan. In the upper horizontalportion of the path of travel ofthe sintering pans, the rollers 17 coactwith horizontal trackways 19 having depending flanges 19 which aresecured to brackets 20 attached to the longitudinal side frame members21, as shown in Fig. 2. At their rear ends, the track members 19 arecurved downwardly in semicircular fashion as shown at 19 and they arearranged to cooperate with upturned semicircular en tremities 22' o'fthe lower track members 22 which are attached to. the vertical framemembers 15. The lower track members'22 are inclined downwardly towardsthe forward end of the machine and arethence curved upwardly in asemicircle, as shown at 22", thus guidingthe sintering pans in theirupward movements at the forward end of' the machine. Each roller 17 hasan annular flange 17f which projects over the edge of the adjacent trackmembers 19 and 22 so that lateral displacement of the sintering pansisprevented. .The movement of the sintering pans 12 on the trackways 19'and 22 is effected vided with teeth 24 arranged in pairs, the

teeth of one pair being spaced apart from those of thenext adjacent pairin such amanner that the teeth will engage behind the rollers 17 onthesintering pans 12, as shown in Fig. 1, when the sintering ans haverolled by gravity from the rear en to the forward end of the machine,whereupon the sintering pans are elevated concentrically with the curvedportions 22'? of the lower trackway and are thus elevated to the forwardend of the upper horizontal trackways 19 where the sintering pans aremoved rearwardl' by the enga ent therewith of the following pans whicfiai re continuously elevated by the driving wheels 24. The driving wheels24 are actuated by a large gear 28 fixed on the shaft 25 and arranged tomesh with a inion 29 I fixed onan auxiliary shaft 30 havmg bear-'ingscarried by vertical frame members 15.

The shaft 30-has fixed thereon a worm wheel 31 meshing with a worm 32attached to the rear end of a longitudinal driving shaft 33. Theshaft.33 is connected at its forward end by bevel gears 34 with atransverse shaft 35 which may be driven by an electric motor or othersuitable driving means. This driving meclianism serves. to actuate thedriving the horizontal wheels 24 in such a manner that the sinteringpans have relatively 'slow travel in a rearward directionon the up erhorizontal trackways 19, as heretofore exp ained. When a sintering pan12 reaches the rear ends of rtions of the trackways 19, it falls byavity through the distance provided b the gap 13, thus discharging themateria s contained-therein.

The sintering ans 12 are provided with upwardly extending side walls 12'connected by transverse bars 12 and the side walls 12" have ledges onwhich are mounted the opposite sides of the grates 123 on which thecrushed ore is ioaded. The sintering pans are open their ends so thatwhen they are arranged in close spaced reiatiou on. the up per trachways19, as shown in it, they form acontinuous trough for the reception ofthe crushed ore. In the region beneath the sintering pans which aremounted on the upper trac ways 19, there is located a casing 3 whichforms a vacuum chamber 38 upper edges of the walls of the casing 3ibeing connected to a rectangular frame 39 which -is seated on. andsecured to the inturned flanges 21 of the side frame members and whichforms a funnel for directing materials downwardly into the chamber 38.The chamber 38 has a'pipe 40 leading from the lower part thereof andconnected to a suction pump or other suitable apparatus adapted formaintaining a vacuum in the chamber 38 so that the sulphur dioxide andother gases which are liberated in the ore. and not the condensed anddeposited therein are drawn downwardly into'the chamber 38 and thenceoutwardly through the pipe 40. In order to form a seal between thevacuum chamber and the sintering pans while these pans are in the upperpart 0 their path of travel, a sealing plate 41, of somewhat flexibleconstruction, is mounted along each lateral ed e of the'frame 39, beinheld in position by c amping members 42 threadedly engagin studs 43. Byadjusting the clamping mem ers 42, the upper edges of the sealing plates41 may be caused to engage in the desired manner the grooves 44 whichare formed in the side members of the sintering pans on the under sidesthereof,

as shown in Fig. 2, in such a manner that the grooves in successive pansali accurately with each other. A seal is 't us formed so that the gasesfrom the sintering pans may be drawn downwardly into the vacuum chamberwithout actual loss.

The crushed and Wetted materials to be a treated in the sintering pansare introduced thereto through a-l'eeding hopper 45 secured to u wardlyprojecting portions of frame mem rs adjacent the orward end of themachine. 'The relatively coarse materials from the discharge of thesintering machine are fed to the inlet end,thereof through an auxiliaryhopper 46 which is mounted adjacent the hopper 45. As the sintering panstravel beneath the hoppers 45 and 46 they are filled so that the uppersurface of the material therein lies flush with the upper edges of theirside walls 12" and, after being filled, the sintering pans m verearwardly on the trackway's 19 and are brought successively intoposition beneath the sintering hood 48 the walls of which extenddownwardly and terminate closely adjacent to the upper surfaces of thesintering pans. The hood48 is lined with refractory material as shown at48 and which the relatively high temperature before referred to isproduced within the sintering hood. After emerging from the sinteringhood, the pans 12' continue their travel rearwardly over the vacuumchamber 38 until,

position so that its lower edge divides the material in the pans along adefinite horizontal plane. If desired, the plate or chute 51 may beadjustable so that ditlerent depths of material may be scraped from thesintering pans. As the pans move rearwardly, the upper portion 52 of thematerial in each pan is pushed upwardly onto the upper-side of the plateor chute 51 and is conveyed up-' wardly thereover by means of aplurality of transverse conveying members 53 which are carried byconveying chains 54. mounted on s rocket gears 55. These gears are fixedon siafts 56, one of which is driven so that the chains 54 are actuatedin the direction indicated by the arrows 57. It will be under-- stoodthat the chutes 51 are inclined upwardly and rearwardly and alsolaterally so that the quantities'of zinc oxide ore which are scrapedupwardly thereover are eventually deposited from the upper end ofthechute 51 into a conduit 58 which is located at one side of themachineand which conveys the zinc oxide ore away for subsequent treatment inseparating the metallic zinc.

Each sintering pain; after passlng the lower end of the device 50, dropsby gravity through the space 13 and thus automatically discharges theremainder of its contents onto a screen 59 located over a hopper 60..Tl1e coarse materials which do not pass through the screen are takenfrom the lower edge of the screen and conveyed by suitable means to thefeeding hopper 46 at the inlet end of the first machine while the finematerials which drop into the hopper 60 are mixed therein with aquantity of carbon, preferably in the "form of anthracite coal andthoroughly wetted with water, preparatory to treatment in a subsequentsmterlng machine of the series.

Between each adjacent pair of sinterlng machines of the apparatusemployed, there is located an elevating device 61 for elevating themixture of discharged material and carbon which drops from the hopper 60into an open vessel 62 where it is picked up by the buckets 63 of theelevating device 61. The buckets 63 are carried by endless chains 64:and are in upright position whencarrled by the upper stretches ofthesechains so that the quantities of materials picked up in the bucketsare conveyed upwardly and thence dumped into the hopper 65 at the upperend or? the elevating device, as shown particularly in Fig. l. Thehopper 65 discharges into a chute 66 which conveys the material to thefeedinghopper 45 of the next sintering machine of the series. The chains64 of the elevating device are mounted to travel on sprocket gears 67andthe sprocket gears at in an inclined position and which may besupported by the frame 14 of the adjacent sintering machine. By thismeans a number of sintering machines, similar to those ordinarilyemployed in the sintering of iron ore, are

adapted for the use of the present process by the application thereto ofthe modified features described above. 4:

Although one example of the improved process of the present inventionand one form of apparatus for carrying on that process have beensetforth above by way of illustration, it will be understood that theimproved process may be practiced in various ways and that various formsof apparatus inay be employed without departing from the scope of theappended claims.

I claim:

1. A process of freeing zinc ores from lead and cadmium containedtherein which comprises subjecting a portion of a body of the ore to atemperature an atmosphere at which lead and cadmium vaporize whilemaintaining another portion of the ore at a substantially lowertemperature whereby the lead and cadmium are volatilized from the firstnamed portion and condensed in the second named portion, and separatingthe two portions.

2. A process of freeing zinc ores from lead and cadmium containedtherein which comprises subjecting a.portion of a body of the ore to atemperature at which lead and cadmium vaporize while maintaining anotherportion of the ore at a substantially lower temperature whereby the leadand cadmium are volatilized from the first named portion and condensedin the second named portion, separating the two portions, and againsubjecting the second named portion to the same process.

3. A process of freeing zinc ores from lead and cadmium containedtherein which comprises subjecting a portion of a body of the ore to atemperature at which lead and cadmium vaporize while maintaining an-lother portion of the ore at a substantially lower temperature wherebythe lead and cad mium are volatilized from the first named portion andcondensed in the second named portion, separating the'two portions,mixing the second named portion with fresh inatcrial and subjecting itto the same process.

42. A. process oi freeing zinc ores "from lead and cadmium containedtherein which comprises subjecting a portion'of a body out the ore to atemperature at which lead and cadmium vaporize while maintaining anotherportion of the ore at a substantiall lower temperature whereby the leadand cad mium are volatilized from the first named portion and condensedin the/second named portion, separating the two portions, screening thesecond named portion andsubjecting the coarser materials thereof to thesame process.

5. The process of purifying zinc ore which consists in crushing andwetting the ore, heating a portion of the body of ore to vaporizecertain ingredients thereof, pausing said vaporized ingredients to becondensed in another portion of the same body of ore, and separating thefirst-mentioned portion of said ore which is thus freed of saidingredients.

6. The process of purifying zinc ore which consists in heating the" oreto vaporize certain ingredients thereof, causing the vaporizedingredients to be withdrawn from a portion of said ore, separating saidportion of said ore, again heating the remaining portion of said ore tovaporize certain ingredients thereof, causing saidlast mentionedvaporized ingredients to be withdrawn from a part of said remainingportion of said ore, and separating said part of said ore from whichsaid vaporized ingredients'are withdrawn. 7

7. The process of purifying zinc ore which consists in placing the orein a conveyor, subjecting the ore to the action of heat while moving insaid conveyor to vaporize certain ingredients thereof, subjecting saidheated ore to the action of suction and causing the vapors to becondensed in the lower part of the moving body of ore, and continuouslyremoving the upper portion of the moving body of ore which is freed ofsaid vaporized ingredients.

8. The process of purifying zinc ore which consists in placing the orein a conveyor, subjecting the ore to the action of heat while moving insaid conveyor to vaporize certain ingredients thereof,v subjecting saidheated ore to the action of suction and causing the vapors to becondensed partly in the lower part of. the moving body of ore,continuously removing the upper ortion of the movin body of ore which is're'ed'of said vaporize ingredients, and extracting the zinc from saidlast mentioned portion of the ore after it has been removed.

9. The process of purifying zinc ore which consists in placing the orein a conveyor, subjecting the ore to the action of heat While moving insaid conveyor to vaporize certain ingredients thereof, subjecting saidheated ore to the action of suction and causing the vapors to becondensed in the lower part of the moving body of ore, continuouslyremoving the" upper portion of the moving body of ore whichis freed ofsaid vaporized 1ngredients, discharging the residue of said ore fromsaid conveyor, mixing carbon with said residue, placing said mixture inanother conveyor, su jecting said mixture in said last mentionedconveyor to the action of heat to vaporize certain ingredientsthereof,then subjecting said mixture to the action of suction and condensingsaid vapors in the lower portion of the moving ore mixture, separatingthe upper portion of the ore mixture from'which said va ors arewithdrawn, and extracting the zinc i separated portion. V

10. The process vof purifying zinc which consists in crushing andwetting the zinc ore placing said ore in a conveyor, causing said ore topass beneatha heating means Whereby certain ingredients of the ore arevaporized, then subjecting the ore to the action of suction meanslocated beneath, the moving body of ore, thereby causing the vapors torom said last mentioned be condensed in the lower portion of the bodyofv ore, then removing the upper layer of the body of ore from which thevaporized ingredients have been withdrawn, and sepawhich is so removed.-

11. The process of purifying zinc ore which'comprises the steps ofcrushing the ore, highly heating the ore to vaporize certain ingredientsthereof while retaining the zinc content of the ore in an unvaporized Istate, causing said vaporized ingredients to consists in crushing t eore, heating the body of the ore to vaporize certain ingredients thereofwhile leaving certain other valuable ingredients unvaporized, causingsaid vaporized ingredients to be condensed in a portion of the same bodyof ore, and separatingthe portion of the ore from which the vaporizeingredients have thus been re moved.

13. The process of purifying zinc ore which comprises the steps ofcrushing the ore, highly heating a portion of the ody of ore to vaporizecertain ingredients thereof while leaving certain other valuableingredients unvaporized and retaining the remaining portion of the oreat a lower temperature, causing said vaporized ingredients to becondensed in said portion of the same body of ore retained at a lowertemperature, and separating the portion of the ore from which thevaporized ingredients have been thus removed.

14. The process of purifying zinc ore whic comprises the steps ofcrushing the ore, heating a portion of the body of the ore while it Isin motion to vaporize certain ingredients thereof while'leaving the zinccontent 90 rating the zinc from the upper layer of'ore of the oreunvaporized and retaining the remaining portion of the body of the oreat a lower temperature, causing said vaporized ingredientsto becondensed in said portion of said ore retained ata lower temperature,and then separating the portion of the ore from which the vaporizedingredients'have been removed While the body of ore is inmotion. 7 r

In testimony whereof I have subscribed my name, r

OSCAR GERLACH.

